Paper products and methods of making the same



Patented Oct. 17, 1950 PAPER PRODUCTS AND METHODS OF MAKING THE SAMECarleton S. Francis, Jn, West Harwich, Mass., assignor, by mesneassignments, to American Viscose Corporation, Wilmington, Del., acorporation of Delaware No Drawing. Application May 25, 1942, Serial No.444,438

This invention relates in general to paper making and in particular to aprocess of making paper and to the paper products so produced andincludes correlated improvements designed to enhance the properties,characteristics, and uses of such products. The expression paper" asemployed in the following specification and in the appended claims isintended to include all waterlaid fibrous products produced from fibreshaving a paper-making length and includes products which are flexible orstiff, thin or thick, soft or hard.

This application is a continuation-in-part of my co-pending applicationSer. No. 300,876, filed October 23, 1939, (now Patent 2,459,803) whichapplication is a continuation-in-part of application Ser. No. 157,018,filed August 2, 1937, now U. S. 2,253,000.

Heretofore in the manufacture of paper it has been customary to rely forstrength almost solely upon the inter-felting of the fibres during thedeposition of the fibres from an aqueous dispersion. It is well knownthat unless great care is used in the proper beating of the pulp, in thefelting, and the calendering of the resulting paper, the productsproduced by conventional paper-making processes are deficient in tearresistance, fold resistance, and bursting strength. Moreover, unlesswater-insoluble sizes are employed for binding the fibres together,paper products made by conventional processes are not resistant totearing when wet.

Heretofore some attempts have been made to bind together the paperfibres in paper products by mixing with the paper fibres a cellulosederivative and thereafter subjecting to heat and pressure or solvents torender the cellulose derivative fibres tacky in an attempt to causethese fibres to fuse or adhere to the non-adhesive paper fibres. Owing,however, to the inherent chemical and physical characteristics ofcellulose derivatives, the products produced by such prior processeshave not been entirely satisfactory. Among other things, cellulosederivatives, such, for example, as cellulose nitrate, cellulose acetate,and the like, are characterized by being inherently non-thermoplastlc,that is, when they are heated, they soften but do not become adhesive ortacky. To render cellulose derivatives truly thermoplastic andadheslvely tacky by heat and pressure alone, it is necessary toincorporate suitable plasticlzer in the cellulose derivative, but theuse of such plasticizers increases the manufacturing difficulties andthe cost of the resulting product. 0n the other hand, when an attempt ismade to render 8 Claims. (Cl. 9221) cellulose derivatives adhesivelytacky by use of organic solvents, it is found that the solvent does notpenetrate the fibrous product uniformly and that when the solventevaporates, there is deposited on the fibres in the product such a thinand friable coating of the cellulose derivative that the resulting bondis insufficient to achieve the correlated objects of the presentinvention.

Moreover, the use of organic solvents in a paper mill creates a firehazard and necessitates the use of solvent recovery equipment foreconomical operation.

It is a general object of the present invention to provide a method forproducing papers which will have improved properties, characteristicsand uses, while avoiding the difiiculties and disadvantages inherent inthe prior processes above described.

It is another object of the invention to provide a paper which ischaracterized by improved tensile strength and increased resistance totearing, folding, bursting and abrasion.

It is a specific object of the present invention to provide a paper inwhich the improved properu ties, characteristics and uses do not dependsolely upon the inter-felting of fibres as is accomplished byconventional methods 01' water-laying paper products, but on thecontrary are due to the presence in the product of a reticulated fibrousstructure extending throughout the mass of the paper product.

Another specific object of the present invention is to provide a paperwhich will show an improved wet tearing strength whereby it is adaptedfor use as a paper towelling or for any use where the product is exposedto the weather, as in building construction and in camouflage.

According to the process of the present invention, papers of improvedproperties, characteristics and uses are made by forming an aqueoussuspension of normally non-adhesive fibres of paper-making length andsynthetic resin fibres which are non-tacky at room temperature but whichbecome tacky below the temperature at which paper-making fibres aredamaged, depositing the mixture of fibres from said suspension in theform of a paper structure, drying and heating the structure to atemperature at which the resin fibres become tacky, and cooling thestructure to effect fibre adhesion. The paper product is preferablysubjected to pressure while the resin is in an adhesive condition. Theexpression paper structure" as used in the claims is intended to includesheets, layers, tubes and molded resin fibres adhesive.

articles of all kinds formed by the separation of the fibre mixture fromits aqueous suspension.

For the paper-making fibres employed in the present invention, there areused any fibres of pape geinaklng length which are not renderedadhesive'y tacky by the treatment that renders the The paper of theinvention may be prepared from any suitable paper-making fibres ofsuitable paper-making length, namely, vegetable fibres such, forexample. as wood, rag fibres, cotton, fiax, jute, straw or other fibresderived from plants of various kinds; mineral fibres such, for example,as glass fibres, rock wool, asbestos, and the like; animal fibres such,for example, as wool, leather fibres, silk fibres, in particular, si kwaste, as well as fibres derived from gelatine, casein, glue, and thelike. The invention includes the use of appropriate mixtures of suchfibres with each other and with textile and cordage wastes. Theexpression "paper-making fibres, as used herein, is intended to includeall fibres adapted to be used in the making of paper, whethernatural-occurring or artificial. When employing vegetable fibres, theymay be prepared for paper-making by any suitable process such, forexample, as the so-called sulphite process, sulphate process, sodaprocess, kraft process or by suitable mechanical processes, andhydrated. bleached, washed, screened, beaten, aged and otherwiseprepared for paper-making in a known manner. The mineral and animalfibres may be suitably purified and prepared for paper-making in a knownmanner.

The potentially adhesive resin fibres are fibres which have an inherenttackiness upon heating to a temperature below that at which thenon-adhesive paper-making fibres are damaged or rendered tacky, such asfibres formed from the copolymers of two or more resin-forming compoundssuch, for example, as co-polymers of vinyl halide and vinyl acetate,co-polymers of vinyl halide and acrylic acid, co-polymers of vinylcompound and styrol compound.

For the thermoplastic fibre, it is preferred to employ the resin fibrebecause such fibres, as compared to the cellulose derivative fibres, aretougher and harder, become tacky at lower temperatures and cool to formtougher and more pliable products. Moreover, the resin/ fibres used arepreferably those which are inert to acids, alkalies and dry-cleaningfluids, and are not waterswelling. Use of such resins preventsdistortion of the adhesive bond under changing atmospheric conditions orin the resence of salts, acids and alkalies, so that the wet and drytensile strength of the adhesive bond will be substantially the same.

The potential y adhesive resin fibres are preformed, extruded fibres andmay be used in the unstretched or pre-stretched condition. However,since stretching tends to increase the cost and to render the resinbrittle after heating, the use of unstretched resin fibres is preferredin the present invention. In the now preferred embodiment, thepotentially adhesive resin fibre used in the present process is alow-melting resin fibre formed from a vinyl copolymer containing lessthan 80% vinyl chloride and the remainder vinyl acetate and having amacro-molecular weight of below 10,000, and which was stretched duringmanufacture less than 70% and which has a heat distortion point below 70C. Using such a resin fibre, porous, flexible and even flufly paperstructures can be produced since little or no appreciable pressure isrequired during activation.

The ratio of synthetic resin fibre to other fibre may also vary widelydepending on the properties of the two types of fibres and may beregulated to suit the purpose for which the paper is destined, but ingeneral a minor proportion, preferably from 3 per cent to 20 per cent ofthe synthetic resin fibre will be employed. Where a greater degree ofstrength or a closer bonding of the component fibres is desired, thepercentage will be relatively high, whereas in papers of certainconstruction where it is desirable to have a comparatively small amountof bonding of the component fibres, the percentage will be relativelysmall.

The non-adhesive paper fibres may be of any length suitable forpaper-making and the length will vary with the type of machine used formixing and sheeting the mixture of fibres. In general, the resin fibreswill have substantially the same length as the non-adhesive fibres, butin some cases where desired, the resin fibres are longer than the otherfibres to aflord more points of adhesion per fibre length and to permitthe manufacture of porous and flexible structures.

The synthetic resin fibre and the paper-making fibre are mixed by amethod suitable to the production of a particular type of paper, forexample, by beating the fibres together in a suitable liquid or byadding the potentially adhesive fibres to the other fibres at any timeprior to sheeting the fibres.

The mixture of paper-making fibres and thermoplastic resin fibres may beformed into a web by a suitable process, for example, by the use ofmachines of various types, such as the Fourdrinier," Harper, singlecylinder or "Yankee multi-vat machine, mould, presse pate," or the like.It is to be understood that the invention is in no way limited to theuse of any particular method or machine.

Generally speaking, in preparing the furnish or load, it is preferableto disperse the non-adhesive paper-making fibres separately in theaqueous dispersion medium, but in some cases the mixture of fibres maybe beaten with water in a conventional manner in a paper pulp beater. Inthe preferred practice the resin fibres are mixed with the other fibresand the mixture stirred, or beaten, only long enough to insure that theresin fibres are substantially uniformly distributed through the fibremass. By adding the resin fibres in this manner, the characteristics ofthe pulp may be properly adjusted by the paper maker without damage tothe resin fibres, and thus the resin fibres can be prevented fromundergoing any undesired physical or chemical changes, or breaking whichmight occur during the mixing or beating operation.

In paper products made heretofore by conventional processes, the fibersare usually bound together by the hydrated or beta cellulose whichresults from the beating of the fibers in water. This beating operationis expensive, time consuming and must be carefully controlled, otherwisethe fibers may be insuificiently hydrated or they may be degraded sothat they lose the greater part of their tensile strength. By thepresent invention it is possible to reduce or eliminate entirely thebeating of the fibers in water, the beater being used merely as a meansfor mixing the paper fibres with the thermoplastic resin fibres. Whenthe resin fibres are rendered tacky by heating, the tacky fibres serveto bind the paper fibres together, the bond being waterproof andnonswelling in water, thus being stronger and more permanent than thebonds produced by hydration of the paper fibres. Accordingly, thepresent invention provides for the production of a novel paper productin which the paper fibres are non-hydrated and un-degraded and boundtogether by waterproof permanent binders resulting from the heating ofthe thermoplastic resin fibres. In the preferred embodiment the resinfibres are bound to the paper fibres throughout the entire length or theresin fibres. If the fibrous structure of the resin fibres is retainedthe product will be porous, however, the activation of the resin fibresmay be suflicient to cause these fibres to lose their structure and forman adhesive which extends throughout the product as a continuous filler,thus rendering the product non-pourous and waterand gas-impermeable.

When paper fibres are unhydrated the activation of the resin fibresshould, in general, be increased to ensure the necessary bonding of thefibres.

The inherent tackiness of the resin fibres is activated by heating thepaper to an appropriate temperature, for example, by the use of dry hotair, contact with heated surfaces, or steam. The temperature of theheat-treatment will depend upon time, pressure and the properties of theresin fibre and must necessarily be below that at which the paper isdamaged. When the paper is cooled, the resin fibres become non-tacky andtough, and adhere to the other fibres, thus providing a paper productwhich possesses increased strength and greater tenacity betweencomponent fibres.

When the paper is made on a Fourdrinier or other continuous type ofpaper-making machine, the resin fibres in the paper may be activatedduring or after drying of the paper; if activated during drying, theresin fibres may be rendered adhesive by means of heated calender rollscooperating with the last rolls of the drying rolls so that the paper isfed to the calender rolls in a pro-heated condition. By this means evenpapers of considerable thickness may be activated and pressedcontinuously in an economical manner.

Where the paper is made on hand screen or by a batch operation, as in amould or cylinder machine, the paper is preferably passed through adryer where it is pre-heated before it is activated. When the paper hasbeen pre-heated to a temperature substantially near the activationtemperature the activation may then be carried out in a continuousmanner as by means of a calender.

The tackiness of the resin fibres may be modified by heating the resinfibres in the presence of a suitable plasticizer depending on theparticular type of resin. The plasticizer may be incorporated in orcarried by the resin fibres and/or by the non-adhesive fibres and may beincorporated in the fibres at any point prior to heating. In thepreferred embodiment the plasticizer is incorporated in the resin massprior to its formation into fibres and filaments. The plasticlzer lowersthe temperature at which the resin fibres are rendered tacky uponheating. After heating, the plasticizer may be allowed to remain or, ifdesired, it may be removed by suitable means, such as evaporation orextraction, thereby preventing the resin fibres from again beingrendered tacky at the original activating temperature and capable ofremaining nontacky at ironing temperatures.

Where the aqueous dispersion medium is recir- 6 culated and reused it ispossible to incorporate plasticizers in the medium either as a solutionor as a suspension.

During the activation of the resin fibres, the paper product may beshaped into a pro-determined form by use of a suitable heated mould. Ifdesired, the wet paper sheet may be shaped into a suitable form and thenheated to dry the product and ultimately to activate the potentiallyadhesive fibres. In this way the pre-determined shape of the paperproduct will be permanently set by the binding of the fibres in theproduct.

The present invention is adapted for making paper products of all kinds,such, for example, as tissue paper, writing paper, book paper. bank notepaper, wrapping paper, news print, boards, including wall boards,building felts, and moulded paper articles of all kinds. The expression"paper product" as used herein is intended to include all articles whichare capable of being fabricated from paper-making fibres in accordancewith the invention.

The properties, characteristics, and uses of the paper produced may bevaried over wide limits depending, interalia, on the nature of thepapermaking fibres, the nature of the potentially adhesive resin fibres,the process of fabrication, the extent of activation of the resinfibres, and the relative proportion of the resin fibres to thepaper-making fibres. With low percentages of resin fibres and/or withmoderate activation of the resin fibres, there may be produced articleshaving a substantial degree of flexibility, but also having an extremetoughness and resistance to folding, all of which are characteristicsnecessary in bank note paper. On the other hand, with greaterpercentages of the resin fibres, as from 10 to 50 per cent, there may beproduced articles which are relatively stiff and resilient, which have ahigh resistance to bursting but which are still capable of being folded,bent, or shaped. Finally, by increasing the amount of resin fibre toabove 50 per cent, there may be produced relatively stiff paper productswhich may be machined with woodworking tools, thus adapting the productsfor use as panels, insulating materials, machine parts, and the like.

It is to be understood that when the percentage of resin fibres issufiiciently high to enable the resin to form a continuous phasethroughout the product or to glaze the surface under the conditions oftemperature and pressure employed, the paper products thus produced willbe impermeable to water and air, which are desirable properties utilizedin a wide variety of fields.

The activation of the resin fibers may be varied in accordance with theproperties desired in the finished products. For example, by merelyheating the resin fibres to that temperature at which they are softenedsufiiciently to. be deformed by the pressure applied, th non-adhesivepaper fibres may be imbedded in the resin fibres although little or noactual adhesion occurs. If the resin fibres are heated to a somewhathigher temperature, that is sufficient to render them tacky, they willbecome bonded to the non-adhesive paper fibres at the points where thefibres cross each other. Under moderate pressure the resin fibres maythus be tacky or bonded to the other fibres at spaced points along thelength of the resin fibres thus producing a three dimensionalreticulated web in the fibre structure. If while the resin fibres aretacky the paper product is subjected to a higher pressure the resinfibres may be bonded along their entire length with the other fibresthus producing a firmer and less porous structure than the structurepreviously described. Finally, at further increased temperatures andpressures, the resin fibres may be melted until they lose their fibrestructure and the adhesive thus produced may be caused to spread throughthe paperproduct in the form of a more or less continuous film whichwill render the product more or less impermeable to gas and water.

One embodiment of the present invention contemplates the use of theproduct as a thermoplastic laminating medium. In such cases, it isessential that the proportion of synthetic resin fibres be sufficient tocause the surfaces of the paper product to present tackiness on heating.The paper manufacturer may. therefore, manufacture the thermoplasticpaper product for sale as a laminating medium prior to the activation ofthe synthetic resin fibres.

By way of illustration, but not by way of limiting the invention therewill be Given the following specific examples:

Example I Ten per cent of synthetic resin fibres, insoluble in water,for example, a low melting resin fibre formed from a vinyl copolymercontaining less than 80% vinyl chloride and the remainder vinyl acetateand having a macromolecular weight of below 10,000 and which wasstretched during manufacture less than 70% and which has a heatdistortion point below 70 C., may be mixed with unbeaten andsubstantially unhydrated papermaking fibres in the beater or in the headbox of the paper machine, the beating being limited to that necessary todisperse the synthetic resin fibres through the paper fibres. Thefurnish or charge is then sheeted in a known manner on a Fourdrinierpaper machine. The

paper sheet is pre-heated on the drying cans and passed, while hotthrough calender rolls positioned at the end of the drying cans, thesheet being heated by such calender to a temperature of 125 C. andsubjected to pressure of 300 pounds per square .inch which renders theresin fibres tacky. Although the product contains unhydrated paperfibres and is porous and flexible, it has a higher wet-tearing andbursting strength than the same sheet in which the resin fibres havenotbeen activated, or similar sheet not containing resin fibres and inwhich the paper fibres are hydrated.

Example H Novel and improved paper board may be made by the followingprocess: of fibres of a copolymer of 90% vinyl chloride and 10% vinylacetate having a melting point of about 150 C. is added to a paperbeater in which the furnish consists of waste newspaper fibres. Theresulting charge is fed into a vat from which the fibres .are suckedupwards against a perforated plate by u e of vacuum to form alayer aboutone-half inch in thickness. The wet sheet is transferred to a belt andpassed beneath the plates of a heat d fiat bed press wherein it issubjected to 300 lbs. of pressure per square inch without heat. Thesheet is then removed from the press and passed through a drying chamberwhere the tempsrature of the sheet is gradually raised to 180 C.whereupon the synthetic resin fibres become tacky and bond to the otherfibres in the product. At the exit of the drying chamber, the sheet ispassed while thuspre-heated through calender 8 rolls to compact thesheet while the synthetic resin fibres are in a tacky condition.Thereafter the sheet is allowed to cool. The resulting product will be arelatively stifi board adapted for use as wall board or for insulation,shoe construction, and the like.

Since certain changes in carrying out the above process, and certainmodifications in the article which embody the invention may be madewithout departing from its scope, it is intended that all mattercontained in the above description shall be interpreted as illustrativeand not in a limiting sense.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

1. In a process for making a paper product, the steps comprising formingan aqueous suspension of cellulosic paper-making fibers of paper-makinglength and water-insoluble preformed, extruded thermoplastic resinfibers oi paper-making length while maintaining said resin fibers infibrous form, said resin fibers being formed from a copolymer of vinylchloride and vinyl acetate and being normally non-tacky, flexible, andtough, and being rendered tacky at a temperature below that at which thepapermaking fibers are damaged; removing water from said suspension todeposit said paper-making and said resin fibers in the form of a paperproduct; and heating said product to efiect a tough. pliable,water-resistant bonding of fibers in said product, without destructionof the fibrous structure of said resin fibers.

2. In a process for making a paper product, the steps comprising formingan aqueous suspension of a mixture of cellulosic fibers of papermakinglength and water-insoluble pre-formed. extruded thermoplastic resinfibers of papermaking length by heating said fibers with water for aperiod sufiicient to mix the fibers uniformly but insumcient to hydratesaid cellulosic fibers substantially and insumcient to destroy thefibrous nature of said resin fibers, said resin fibers being formed froma copolymer of vinyl chloride and vinyl acetate and being normallynon-tacky, flexible, and tough, and being rendered tacky at atemperature below that at which the papermaking fibers are damaged;removing water from said suspension to deposit said fibers in the formof a paper product comprising said paper-making fibers and said resinfibers; and heating said product to eflect a tough, pliable,water-resistant bonding of fibers in said product, without destructionof the fibrous structure of said resin fibers.

3. In a process for making a molded paper product, the steps comprisingforming an aqueous suspension of a mixture of paper-making fibers ofpaper-making length and water-insoluble preformed, extrudedthermoplastic resin fibers of paper-making length while maintaining saidresin fibers in fibrous form, said resin fibers being formed from acopolymer of vinyl chloride and vinyl acetate and being normallynon-tacky, flexible, and tough, and being rendered tacky at atemperature below that at which the papermaking fibers are damaged;removing a mixture of said paper-making and said resin fibers from saidsuspension in the form of a shaped structure by the use of a mold; andheating said structure to efl'ect a tough, pliable. water-resistantbonding of fibers in said product, without destruction of the fibrousstructure of said resin fibers.

4. As an article of manufacture, a. paper product comprising water-laidpaper-making fibers and water-insoluble pre-iormed, extruded,thermoplastic resin fibers formed from a copolymer of vinyl chloride andvinyl acetate, said resin fibers being normally non-tacky, flexible, andtough, and being rendered tacky at a temperature below that at which thepaper-making fibers are damaged, fibers in said product being bonded toeach other due to the thermal tackiness alter heating of said resinfibers.

5. As an article of manufacture, a paper product comprising a water-laidmixture or cellulosic paper-making fibers and water-insoluble pretormed,extruded, thermoplastic resin fibers formed from a copolymer of vinylchloride and vinyl acetate, said resin fibers being normally non-tacky,flexible, and tough. and being rendered tacky at a temperature belowthat at which the paper-making fibers are damaged, fibers in saidproduct being bonded to each other due to the thermal tackiness afterheatin of said resin fibers.

6. As an article manuiacture, a paper product comprising a water-laidmixture of substantially unhydrated celluloslc paper-making fibers andwater-insoluble pre-iormed, extruded, thermoplastic resin fibers formedfrom a ccpolymer or vinyl chloride and vinyl acetate, said resin fibersbeing normally non-tacky, flexible, and tough, and being rendered tackyat a temperature below that at which the paper-making fibers aredamaged, fibers in said product being bonded to each other substantiallysolely due to the thermal tackiness after heating 0! said resin fibers.

7. In a process for making a paper product, the step comprisingwater-laying paper-making fibers of paper-making length andwater-insoluble pre-formed, extruded thermoplastic resin fibers oipaper-making length while maintaining said resin fibers in fibrous formto form a paper product comprising said aper-making fibers and saidresin fibers and adapted to be heated to render said resin fibers tackyand to efiect bonding of fibers in said product by the thermoplasticmaterial of said resin fibers; the said resin fibers being tormed oi. acopolymer oi. vinyl chloride and vinyl acetate and being normallynon-tacky,

10 flexible, and tough, and being-rendered tacky at a temperature belowthat at which the papermaking fibers are damaged.

8. As an article of manufacture. a paper product comprising water-laidpaper-making fibers and water-insoluble pre-i'crmed, extruded,thermoplastic resin fibers formed from a ccpolymer oi vinyl chloride andvinyl acetate, said resin fibers being normally non-tacky, flexible, andtough, and capable of being rendered tacky at a temperature below thatat which the papermaking fibers are damaged to provide a product inwhich fibers in said product are bonded by the thermoplastic material 0!said resin fibers.

CARLETON S. FRANCIS. J a.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,829,585 Dreyfus et al Oct. 27,1931 1,919,697 Grofi July 25, 1933 2,031,606 Johnston Feb. 25, 19362,038,679 Richter Apr. 28, 1936 2,069,771 Pascoe et al Feb. 9, 19372,140,048 Fikentscher et al. Dec. 13, 1938 2,156,455 Kleine et al May 2.1939 2,253,000 Francis Aug. 19, 1941 2,277,049 Reed Mar. 24, 19422,278,896 Rugeley et al. Apr. 7, 1942 3,306,731 Francis Dec. 29, 19422,459,803 Francis Jan. 25, 1949 FOREIGN PATENTS Number Country Date148,780 Austria Mar. 10, 1937 806,524 France Dec. 18, 1936 301,428 GreatBritain Jan. 30, 1930 301,807 Great Britain Jan. 30, 1930 458,802 GreatBritain Dec. 28. 1936 371,876 Germany May 23, 1923 OTHER REFERENCESRayon Textile Monthly, June 1946, p. 51.

1. IN A PROCESS FOR MAKING A PAPER PRODUCT, THE STEPS COMPRISING FORMINGAN AQUEOUS SUSPENSION OF CELLULOSIC PAPER-MAKING FIBERS OF PAPER-MAKINGLENGTH AND WATER-INSOLUBLE PREFORMED, EXTRUDED THERMOPLASTIC RESINFIBERS OF PAPER-MAKING LENGTH WHILE MAINTAINING SAID RESIN FIBERS INFIBROUS FORM, SAID RESIN FIBERS BEING FORMED FROM A COPOLYMER OF VINYLCHLORIDE AND VINYL ACETATE AND BEING NORMALLY NON-TACKY, FLEXIBLE, ANDTOIUCH, AND BEING RENDERED TACKY AT A TEMPERATURE BELOW THAT AT WHICHTHE PAPERMAKING FIBERS ARE DAMAGED; REMOVING WATER FROM SAID SUSPENSIONTO DEPOSIT SAID PAPER-MAKING AND SAID RESIN FIBERS IN THE FORM OF APAPER PRODUCT; AND HEATING SAID PRODUCT TO EFFECT A TOUGH, PLIABLE,WATER-RESISTANT BONDING OF FIBERS IN SAID PRODUCT, WITHOUT DESTRUCTIONOF THE FIBROUS STRUCTURE OF SAID RESIN FIBERS.